1. Field of the Invention
The present invention relates to multilayer flexographic printing plates and particularly to primer layers in such plates.
2. Background of the Invention
Flexography is a term that broadly applies to a printing format which uses a flexible substrate bearing an elastomeric or rubbery relief printing surface.
The first flexographic printing plates were produced from natural or synthetic rubber compositions which were cured chemically under heat and pressure in a mold utilizing conventional rubber curatives such as mercapto compounds (Flexography: Principles and Practices, 3rd Edition, Flexographic Technical Association, p. 158-162). More recently, photopolymer elastomeric compositions (elastomer containing compositions curable upon exposure to actinic radiation) have been used to produce relief printing plates. For example, U.S. Pat. No. 4,162,919 describes the use of a photosensitive composition containing a block copolymer as an elastomeric polymeric binder, a compatible ethylenically unsaturated monomer, and a photoinitiator. Similarly, British Patent 1,454,191 describes the use of an elastomeric polyurethane based photosensitive layer. In both cases, the standard solvent wash procedure is used to develop the relief layer after exposure to actinic radiation. European Patent 261,910 describes a water-developable flexographic printing plate. U.S. Pat. No. 5,015,556 discloses a thermal developable system.
Aziridine functional materials have been used to improve bonding between various types of materials. For example, aziridine functional materials have been incorporated into functional coatings (e.g., reflective layers, antihalation layers, etc.) which contain groups reactive with the aziridine functionality. These coatings are then applied to a substrate. See, for example, U.S. Pat. Nos. 3,017,280; 4,167,414; 4,181,528; and 4,241,169.
U.S. Pat. No. 3,704,167 discloses the use of polyaziridine-functional materials to improve the adhesion of a subsequently applied magnetic recording layer to an antihalation layer on motion picture film.
U.S. Pat. No. 4,749,617 discloses a composite article wherein two rigid materials are joined to one another via an intermediate layer made up of an aziridine-functional material and an organic resin.
U.S. Pat. No. 5,057,371 discloses the application of a composition, consisting essentially of at least one aziridine functionality or group, to a substrate. Subsequently applied layers of magnetic recording media, photographic layers, adhesives, radiation sensitive compositions and silanes may be applied to the aziridine-treated surface.
U.S. Pat. No. 4,939,008 describes an aziridine functional layer which is used to bond a polyolefin layer to a polymeric substrate.
U.S. Pat. No. 5,187,044 describes use of an aziridine functional composition as a primer layer on a flexible substrate to which a photosensitive polyurethane composition is then applied to form a flexographic printing plate.